diff --git a/FluentValidation.AutoValidation.Shared/src/Extensions/TypeExtensions.cs b/FluentValidation.AutoValidation.Shared/src/Extensions/TypeExtensions.cs
index 3d406e2..019bd3c 100644
--- a/FluentValidation.AutoValidation.Shared/src/Extensions/TypeExtensions.cs
+++ b/FluentValidation.AutoValidation.Shared/src/Extensions/TypeExtensions.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -32,6 +33,13 @@ public static bool IsCustomType(this Type? type)
                 return false;
             }
 
+            if (typeof(IEnumerable).IsAssignableFrom(type))
+            {
+                var underlyingType = type.IsArray ? type.GetElementType() : type.GetGenericArguments().LastOrDefault();
+
+                return underlyingType != null && underlyingType.IsCustomType();
+            }
+
             return type.IsClass || type.IsValueType;
         }
 
diff --git a/Tests/src/FluentValidation.AutoValidation.Shared/Extensions/TypeExtensionsTest.cs b/Tests/src/FluentValidation.AutoValidation.Shared/Extensions/TypeExtensionsTest.cs
index 3920f6c..d99daa0 100644
--- a/Tests/src/FluentValidation.AutoValidation.Shared/Extensions/TypeExtensionsTest.cs
+++ b/Tests/src/FluentValidation.AutoValidation.Shared/Extensions/TypeExtensionsTest.cs
@@ -1,6 +1,7 @@
 // ReSharper disable InconsistentNaming
 
 using System;
+using System.Collections.Generic;
 using Microsoft.AspNetCore.Mvc;
 using SharpGrip.FluentValidation.AutoValidation.Mvc.Attributes;
 using SharpGrip.FluentValidation.AutoValidation.Shared.Extensions;
@@ -42,6 +43,87 @@ public void Test_IsCustomType()
         Assert.False(typeof(Uri).IsCustomType());
     }
 
+    [Fact]
+    public void Test_IsCustomType_Collections()
+    {
+        Assert.True(typeof(ICollection<TestModelClass>).IsCustomType());
+        Assert.True(typeof(ICollection<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(ICollection<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(ICollection<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(ICollection<Enum>).IsCustomType());
+        Assert.False(typeof(ICollection<string>).IsCustomType());
+
+        Assert.True(typeof(IList<TestModelClass>).IsCustomType());
+        Assert.True(typeof(IList<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(IList<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(IList<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(IList<Enum>).IsCustomType());
+        Assert.False(typeof(IList<string>).IsCustomType());
+
+        Assert.True(typeof(List<TestModelClass>).IsCustomType());
+        Assert.True(typeof(List<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(List<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(List<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(List<Enum>).IsCustomType());
+        Assert.False(typeof(List<string>).IsCustomType());
+
+        Assert.True(typeof(TestModelClass[]).IsCustomType());
+        Assert.True(typeof(TestModelRecord[]).IsCustomType());
+        Assert.True(typeof(TestModelStruct[]).IsCustomType());
+        Assert.False(typeof(TestModelEnum[]).IsCustomType());
+        Assert.False(typeof(Enum[]).IsCustomType());
+        Assert.False(typeof(string[]).IsCustomType());
+
+        Assert.True(typeof(Dictionary<string, TestModelClass>).IsCustomType());
+        Assert.True(typeof(Dictionary<string, TestModelRecord>).IsCustomType());
+        Assert.True(typeof(Dictionary<string, TestModelStruct>).IsCustomType());
+        Assert.False(typeof(Dictionary<string, TestModelEnum>).IsCustomType());
+        Assert.False(typeof(Dictionary<string, Enum>).IsCustomType());
+        Assert.False(typeof(Dictionary<string, string>).IsCustomType());
+
+        Assert.True(typeof(HashSet<TestModelClass>).IsCustomType());
+        Assert.True(typeof(HashSet<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(HashSet<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(HashSet<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(HashSet<Enum>).IsCustomType());
+        Assert.False(typeof(HashSet<string>).IsCustomType());
+
+        Assert.True(typeof(IEnumerable<TestModelClass>).IsCustomType());
+        Assert.True(typeof(IEnumerable<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(IEnumerable<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(IEnumerable<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(IEnumerable<Enum>).IsCustomType());
+        Assert.False(typeof(IEnumerable<string>).IsCustomType());
+
+        Assert.True(typeof(IReadOnlyList<TestModelClass>).IsCustomType());
+        Assert.True(typeof(IReadOnlyList<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(IReadOnlyList<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(IReadOnlyList<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(IReadOnlyList<Enum>).IsCustomType());
+        Assert.False(typeof(IReadOnlyList<string>).IsCustomType());
+
+        Assert.True(typeof(IReadOnlyCollection<TestModelClass>).IsCustomType());
+        Assert.True(typeof(IReadOnlyCollection<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(IReadOnlyCollection<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(IReadOnlyCollection<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(IReadOnlyCollection<Enum>).IsCustomType());
+        Assert.False(typeof(IReadOnlyCollection<string>).IsCustomType());
+
+        Assert.True(typeof(ISet<TestModelClass>).IsCustomType());
+        Assert.True(typeof(ISet<TestModelRecord>).IsCustomType());
+        Assert.True(typeof(ISet<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(ISet<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(ISet<Enum>).IsCustomType());
+        Assert.False(typeof(ISet<string>).IsCustomType());
+
+        Assert.False(typeof(IAsyncEnumerable<TestModelClass>).IsCustomType());
+        Assert.False(typeof(IAsyncEnumerable<TestModelRecord>).IsCustomType());
+        Assert.False(typeof(IAsyncEnumerable<TestModelStruct>).IsCustomType());
+        Assert.False(typeof(IAsyncEnumerable<TestModelEnum>).IsCustomType());
+        Assert.False(typeof(IAsyncEnumerable<Enum>).IsCustomType());
+        Assert.False(typeof(IAsyncEnumerable<string>).IsCustomType());
+    }
+
     [Fact]
     public void Test_HasCustomAttribute()
     {